Stone in part of Stonehenge, massive (3)
I believe the answer is:
gem
'stone' is the definition.
(thesaurus)
'part of stonehenge massive' is the wordplay.
'part of' indicates the answer is hidden within the clue.
'GEM' is hidden in the letters of 'stonehenge massive'.
'in' acts as a link.
(Other definitions for gem that I've seen before include "Valued person; jewel" , "Pearl" , "Kindness; comfort (German)" , "A jewel of an Orangeman" , "Pleasant and cheerful (from German)" .)